The present invention is directed to pumps and shut off valves and, more particularly, to pumps and shut off valves for use in reverse osmosis water purification systems.
In reverse osmosis water purification systems, the feed water to be purified is supplied under pressure to one side of a reverse osmosis membrane in a pressure vessel and a pressure differential is maintained across the membrane. This differential drives the water in the feed water through the membrane to produce the desired purified permeate. A substantial percentage of the feed water input to the pressure vessel is bypassed and discharged through a flow restrictor to continuously purge the feed side of the membrane. The magnitude of the pressure differential across the membrane is important because it has a direct function on the rate and amount of water that may be purified in any given amount of time. The greater the pressure differential, the greater the amount of permeate produced per given amount of time. In view of the foregoing, it will be appreciated that for a given pressure of feed supply to be purified, it will therefore be desirable to reduce the level of back pressure on the permeate or discharge side of the membrane. Assuming a given supply pressure, each increment that the back pressure may be reduced will result in an increased rate and volume of production of permeate.
Reverse osmosis permeate pumps have been developed which are capable of reducing the back pressure to somewhat less than 5 psi. One such pump is disclosed in U.S. Pat. No. 5,460,716. It employs a diaphragm which defines a pumping chamber on one side for pumping the permeate and a working chamber on the other side which is connected to the feed water which is being bypassed. Valves are positioned to alternately admit the bypassed feed water to the working chamber of the pump and then drain it to set up a pumping action in the pumping chamber to pump the permeate. The disadvantages of such a pump is its relatively large size, its relatively discontinuous operation and the fact that back pressure reduction to only about 5 psi is possible.
Permeate reverse osmosis pumps with shut off valves constructed in accordance with the present invention are surprisingly capable of further substantial reductions in the back pressure in a reverse osmosis system and, thereby, a substantial increase in the pressure drop across the membrane with its accompanying advantages. In the pumps and shut off valves of the present invention, the back pressure may actually be reduced to zero and in many cases as low as substantial negative pressure. This, of course, results in a substantial increase in rate of production of permeate compared to the prior systems having a back pressure reduction of only down to about 5 psi. Moreover, in the pumps and shut off valves of the present invention, the size and pumping capacity of the pump may be reduced to as little as a quarter to a half of the prior pumps, the pumping of permeate is substantially continuous rather than discontinuous, and bypass feed and drain valves of the prior systems are substantially eliminated. Moreover, a separate source of electrical or other energy is not necessary in one of the pump and shut off valve embodiments of the present invention, and the valve may be readily operated simply by the feed bypass from the pressure vessel which is to be discharged to a drain anyway, and which provides ample driving power for the embodiment of the pump and shut off valve of the present invention. In another embodiment of pump and shut off valve of the present invention, the pump may be powered by a source of energy other than the bypassed brine and is capable of producing substantial negative pressures across the membrane of much larger magnitude than were previously known while enjoying a substantial reduction in pump size and capacity.
In one principal aspect of the present invention, a pump and shut off valve comprise a pumping compartment, a feed supply compartment and a drive including a drive shaft which is driven by the drive and extends into the pumping compartment. A piston in the pumping compartment divides the pumping compartment into first and second chambers, and a drive transmitting connector extends between the drive shaft and the piston to reciprocally move the piston toward and away from the first and second chambers, respectively, to alternately increase and decrease the volume in the respective chambers. First and second fluid inlets for introducing a fluid to the first and second chambers, respectively, and first and second fluid discharges for discharging the fluid from the first and second chambers, respectively, are also provided. A check valve in each of the first and second fluid inlets permits the flow of fluid to each of the chambers, but prevents the flow from each of the chambers, a check valve in each of the first and second fluid discharges permits the flow of fluid from each of the chambers, but prevents the flow to each of the chambers, and the first and second discharges communicate with the feed supply compartment. A fluid inlet to the feed supply compartment for introducing a fluid to the feed supply compartment and a fluid discharge from the feed supply compartment for discharging the fluid from the feed supply compartment are also provided. A valve in the feed supply compartment is movable in response to a decreased fluid pressure in the first and second discharges from the first and second chambers to permit the flow of fluid between the fluid inlet and discharge of the feed supply compartment, and in response to an increased fluid pressure in the first and second discharges from the first and second chambers to block the flow of fluid between the fluid inlet and discharge of the feed supply compartment.
In another principal aspect of the present invention, the check valve in the first inlet and the check valve in the second discharge close and fluid is discharged from the first chamber through the first discharge and introduced to the second chamber through the second inlet when the piston moves toward the first chamber, and the check valve in the second inlet and the check valve in the first discharge close and fluid is discharged from the second chamber through the second discharge and introduced to the first chamber through the first inlet when the piston moves toward the second chamber.
In still another principal aspect of the present invention, the aforementioned pump and shut off valve includes a drive compartment, a first fluid inlet to the drive compartment for introducing a fluid to the drive compartment, and a fluid discharge from the drive compartment for discharging the fluid from the drive compartment. The drive is positioned in the drive compartment and includes a drive mechanism which is driven by contact with the fluid which passes through the drive compartment. A transmission which is powered by the drive mechanism and which drives the drive shaft.
In still another principal aspect of the present invention, the drive mechanism comprises a wheel which is rotated by the fluid which passes through the drive compartment, and the transmission is a gear set.
In still another principal aspect of the present invention, the drive includes a motor which is coupled to the drive shaft to drive it.
In still another principal aspect of the present invention, the drive transmitting connector is a crank arm.
In still another principal aspect of the present invention, the valve in the feed supply compartment comprises a piston which moves reciprocally in the compartment between a first position in which the flow of fluid between the fluid inlet and discharge of the third compartment is permitted, and a second position in which the flow of fluid between the fluid inlet and discharge of the feed supply compartment is blocked.
In still another principal aspect of the present invention, a spring is positioned in the third compartment which urges the valve toward the first position in one embodiment and toward the second position in another embodiment.
In still another principal aspect of the present invention, the pump and shut off valve are in combination with a reverse osmosis water purification system which includes a reverse osmosis membrane in a pressure vessel having a feed inlet, a feed discharge and a permeate discharge, and a tank for receiving the permeate from the permeate discharge, and wherein a source of feed to be purified communicates with the fluid inlet to the feed supply compartment, the feed to be purified from the fluid discharge from the feed supply compartment communicates with the feed inlet of the vessel, the permeate from the permeate discharge of the vessel communicates with the first and second fluid inlets for introducing fluid to the first and second chambers, and the permeate from the first and second fluid discharges for discharging the fluid from the first and second chambers, respectively, communicates with the tank.
In still another principal aspect of the present invention, in the last mentioned combination with a reverse osmosis purification system, the feed discharge of the vessel communicates with the earlier mentioned drive compartment to drive the drive.
In still another principal aspect of the present invention, the valve shuts off the feed to be purified when the tank is full of permeate and increases in pressure.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.